Processing aid for polymers

ABSTRACT

Polymer blend composition having improved processibility and comprising: 
     (a) a major portion of a difficultly melt-processible polymer, and 
     (b) a minor portion of: 
     (1) at least an effective amount, to improve processibility, of a fluorocarbon copolymer which at the melt-processing temperature of (a) is either in a melted form if crystalline, or is above its glass transition temperature if amorphous, and 
     (2) at least an effective amount, to improve processibility, of at least one tetrafluoroethylene homopolymer or copolymer of tetrafluoroethylene and at least one monomer copolymerizable therewith, wherein the mole ratio of fluorine to hydrogen is at least 1:1, and which is solid at the melt-processing temperature of (a); 
     masterbatches comprised of the processing aid; and processes utilizing the processing aid.

FIELD OF THE INVENTION

The present invention relates to a processing aid for polymers, and topolymers having improved processibility, particularly improved extrusioncharacteristics.

BACKGROUND

The melt extrusion of high molecular weight polymers, for example,hydrocarbon polymers, into shaped structures such as tubing, pipe, wirecoating or film is accomplished by well-known procedures wherein arotating screw pushes a heated, molten and viscous polymer melt throughthe extruder barrel into a die in which the polymer is shaped to thedesired form and is then subsequently cooled and resolidified, byvarious means, into the general shape of the die.

In order to achieve low production costs it is desirable to extrude athigh rates. Although the extrusion rate is readily increased byincreasing the rate of revolution of the extruder screw, there is atechnical limit to these increases because of the viscoelasticproperties of the polymer. At rates above this limit the polymer may bemechanically heated to temperatures at which thermal decomposition canoccur, or extrudates with a rough surface are obtained. The latterphenomenon can generate an undesirable pattern on the surface of theextrudate. One way of avoiding this occurrence is to extrude at a highertemperature, but this adds to the processing costs and makes cooling ofthe extrudate more difficult. More seriously many polyolefins arealready extruded at temperatures near their decomposition temperatures,and further increases are not feasible.

It is desirable, therefore, to find highly efficient means of increasingthe extrusion rate, without raising the melt temperature, whileproducing products with smooth surfaces. Changes in extruder and dieconfiguration can improve melt flow but are not always practical oreconomically feasible Another approach involves the addition ofconventional wax-type process aids which reduce bulk viscosity and insome cases improve processing properties. However, the efficiency ismarginal and the high levels of additive required often adversely affectother properties. In Blatz, U.S. Pat. No. 3,125,547, it is disclosedthat the use of 0.01-2.0 wt. % of a fluorocarbon polymer that is in afluid state at process temperature, such as a fluoroelastomer, willreduce die pressure and significantly increase the extrusion rate atwhich melt fracture occurs for high and low density polyethylenes andother polyolefins. It is further taught in U.S. Pat. No. 3,125,547 thatfluororesins which are solids at process temperature afford little or noimprovements in extrusion characteristics of hydrocarbon polymers. Bythe term solid, it is meant that the fluororesin, if crystalline innature, is not melted, or, if amorphous in nature, is not above theglass transition temperature.

Kamiya and Inui, in Japanese Patent Application Publication Kokoku No.45-30574 (1970, examined) cite the use of crystalline fluorocarbonpolymers at temperatures below their melting points to eliminate diebuild-up but say nothing of other extrusion improvements. Nishida, Tateand Kitani, in Japanese Patent Application Publication Kokai No.62-64847, disclose injection molding compositions comprising anethylene/alpha olefin copolymer having an MFR Of 0.2-200 g/10 min., adensity of 0.850-0.945 g/cm3, and a Q value of 2.5-12, and 0.001-1% byweight of a fluorinated hydrocarbon polymer having an F/C ratio of atleast 1:2.

Chu, in U.S. Pat. No. 4,740,341, discloses blends having improvedextrudability and comprising a linear polymer of ethylene havingincorporated therein 0.01-0.5 wt. %, based on the composition, of afluorocarbon polymer having an F/C ratio of at least 1:2 and which isfluid at 120°-300° C., and 0.01-0.5 wt. %, based on the composition, ofa polysiloxane.

Larsen, in U.S. Pat. No. 3,334,157, discloses polyethylene which hasbeen modified to improve its optical properties by incorporating therein0.015 to greater than 1.7 % by wt., based on the mixture, of finelydivided polytetrafluoroethylene.

It is an object of this invention to provide resin compositions withsubstantially improved extrusion characteristics. It is another objectto provide polymers which can be extruded at high rates to giveextrudates of high surface quality. It is yet another object to providepolymers that can be extruded at low die pressures and at low melttemperatures. Another object is to provide a processing aid by means ofwhich all the above can be achieved. A further object is to providemasterbatches of the processing aid. A still further object is toprovide all the above with particular emphasis on high molecular weighthydrocarbon polymers which are susceptible to melt processingdifficulties of the type discussed above. Other objects will becomeapparent hereinafter.

SUMMARY OF THE INVENTION The present invention provides a processing aidcomposition for difficultly melt-processible polymers. The processingaid consists essentially of, with the parts totaling 100%:

(a) 2-95 parts by weight of a fluorocarbon copolymer which at themelt-processing temperature of the difficultly melt-processible polymeris either in a melted form if crystalline or is above its glasstransition temperature if amorphous; and

(b) 98-5 parts by weight of a tetrafluoroethylene homopolymer orcopolymer of tetrafluoroethylene and a monomer which is copolymerizabletherewith, wherein the mole ratio of fluorine to hydrogen is at least1:1, and which is solid at the melt-processing temperature of thedifficultly melt-processible polymer.

The processing aid composition consists essentially of a minor portionof the processing aid and a major portion of a polymer, either amelt-processible or difficultly melt-processible polymer, or both, forexample, a hydrocarbon polymer.

The present invention also provides a polymer blend composition havingimproved processibility and which comprises:

(a) a major portion of a difficultly melt-processible polymer, the hostpolymer, for example, a high molecular weight hydrocarbon homopolymer orcopolymer of one or more hydrocarbon monomers, and

(b) a minor portion of:

(1) at least an effective amount to improve processibility, preferablyto about 0.5 wt. %, based on the weight of (a), more preferably0.002-0.08 wt. %, of a fluorocarbon copolymer wherein, preferably, themole ratio of fluorine to hydrogen is at least 1:1.5, which at themelt-processing temperature of (a) is either in a melted form ifcrystalline, or is above its glass transition temperature if amorphous,and

(2) at least an effective amount to improve processibility, preferably0.002-0.08 wt. %, based on the weight of (a), of at least onetetrafluoroethylene homopolymer or copolymer of tetrafluoroethylene andat least one monomer copolymerizable therewith, wherein the mole ratioof fluorine to hydrogen is at least 1:1, and which is solid at themelt-processing temperature of (a).

For example, when the host polymer (a) is a hydrocarbon polymer, itsmelt-processing temperature generally will be in the range 100°-250° C.

Finally, the invention provides masterbatches containing the aforesaidprocessing aid; it provides processes for facilitating the processing ofdifficultly melt-processible polymers; and it provides difficultlymelt-processible polymers containing the processing aid.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure which is a part of this specification is a plot of diepressure (MPa) vs throughput (g/minute), showing the superior resultsachieved by means of this invention, as compared to those achieved bymeans of the prior art.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention it has been discovered,surprisingly, that for the improvement of extrusion behavior,difficultly melt-processible polymers which contain combinations offluorocarbon polymers (hereinafter called type (1) fluorocarbonpolymers) that are above their melting points if crystalline, or abovetheir glass transition temperatures if amorphous, and are thus moltenand fluid at the polymer-processing temperatures, and crystalline oramorphous fluorocarbon polymers (herinafter called type (2) fluorocarbonpolymers) that are solid at the polymer melt-processing temperatures,have significant advantage over such difficultly melt-processiblepolymers which contain equivalent, or even greater, amounts ofextrusion-modifying additives of the art, as in U.S. Pat. No. 3,125,547(supra). The term "extrusion behavior" is intended to include suchparameters as the die pressure reached during extrusion, the operatingmelt temperatures and the maximum extrusion rates that can be achievedwhile maintaining melt stability and good extrudate surface quality.Thus, the compositions of this invention have much improved extrusionbehavior, that is, reduced die pressure, higher allowable extrusionrates, and enhanced surface smoothness of extruded articles, and also,in the case of blown films, improved clarity, compared to polymers notcontaining types (1) and (2) fluorocarbon polymers.

The fluorocarbon polymers of type (1) are those that are fluid at themelt-processing temperature of the difficultly melt-processible polymer.Thus, at processing temperature they must be above their melting pointif crystalline, or above their glass transition temperature ifamorphous. Hence, the melting or softening point of these polymerspreferably should be in the range 120° to 300° C. or below, morepreferably, in the range 120° to 200° C. or below. The polymers shouldhave sufficiently high molecular weight, with number average molecularweights greater than about 10,000, such that they do not exude from thedifficultly melt-processible polymer extrudate at melt-processingtemperatures. With respect to their chemical composition, it ispreferred, but not essential, to employ fluorocarbon polymers having afluorine to hydrogen ratio of at least 1:1.5. Fluorinated monomers whichgive rise to suitable polymers include vinylidene fluoride,hexafluoropropylene, chlorotrifluoroethylene, tetrafluoroethylene andperfluoroalkyl perfluorovinyl ethers. Specific examples of thefluorocarbon polymers of type (1) that may be employed in this inventioninclude copolymers of vinylidene fluoride and a monomer selected fromhexafluoropropylene, chlorotrifluoroethylene, 1-hydropentafluoropropylene and 2-hydropentafluoropropylene; copolymersof vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene or1- or 2-hydropentafluoropropylene; copolymers of tetrafluoroethylene andpropylene and, optionally, vinylidene fluoride, all of which are knownin the art. In some cases these copolymers may also include abromo-containing monomer as taught in Apotheker and Krusic, U.S. Pat.No. 4,035,565, or terminal iodo-groups, as taught in U.S. Pat. No.4,243,770. The latter patent also discloses the use of iodogroup-containing fluoroolefin comonomers. When certain molar ratios ofmonomers are used in these copolymers, then the glass transitiontemperature is near or below 0° C., and these polymers are usefulelastomers that are readily available articles of commerce.

The fluorocarbon polymers of type (2) that are solid at the meltprocessing temperature of the difficultly melt-processible polymerinclude homopolymers of tetrafluoroethylene and copolymers oftetrafluoroethylene with certain copolymerizable monomers. The selectionof the fluorocarbon polymer of type (2) is not limited to high molecularweight polymers, whether the polymer is melt-processible or notmelt-processible, whether the polymer is made by dispersionpolymerization or suspension polymerization, or how much comonomer ispresent, except as stated above. For example, if excessive amounts ofcomonomer are used, the polymer will not be a solid at the temperatureused for melt processing the difficultly melt-processible polymer; or,if a copolymer has too low a molecular weight, the copolymer may not bea solid at the temperature used for melt processing the difficultlymelt-processible polymer. Suitable tetrafluoroethylene homopolymersinclude those that are high molecular weight and fibrillate, or do notfibrillate to a substantial extent, under shearing conditions, as wellas those which are low molecular weight and non-fibrillating, such asthose which have been subjected to ionizing radiation. Suitable monomerscopolymerizable with tetrafluoroethylene to give melt-processiblecopolymers are ethylene, perfluoroolefins such as hexafluoropropylene,and perfluoro(alkyl vinyl ethers) such as perfluoro(propyl vinyl ether)and perfluoro(alkyl ethers) which contain functional groups such as--SO₂ F or --COOCH₃. More than one comonomer may be used, provided allthe aforesaid requirements are met.

The effect of the combined addition of fluorocarbon polymers types (1)and (2) in eliminating roughness of the extrudate, allowing increases inextrusion speed and reducing die pressures is significantly greater thanwhen either type (1) or type (2) is used alone at concentrations equalto the sum of the concentrations of (1) and (2). It has been found thateven when (1) and (2) are added at total concentrations as low as 0.0025wt. %, all extrudate roughness is eliminated at extrusion shear rateswell beyond 1000 sec⁻¹ (Example 2). Quantities in excess of 1 wt. % arenot necessary. In general, if the fluorocarbon polymers are notcompatible with the difficultly melt-processible polymer, that is tosay, are not soluble in such polymer, the addition of higher levelsserves no useful purpose, and when the incompatible fraction becomes toolarge, it may adversely affect the optical properties of the extrudate.Such is the case, for example, when the difficultly melt-processiblepolymer is a hydrocarbon polymer. The beneficial effects of even verylow ratios of types (1) to (2) or types (2) to (1) are readily evidentbut, in general, there will be an optimum ratio of types (1) to (2)which may be determined experimentally for any particular combination oftypes (1) and (2). The weight ratio of fluorocarbon polymer type (1) tofluorocarbon polymer type (2) may vary from 2/98 to 95/5, preferablyfrom 10/90 to 90/10.

When the difficultly melt-processible polymer is a hydrocarbon polymer,for example, a hydrocarbon polymer having a melt index (ASTM D-1238) at190° C. of 5.0 or less, preferably 2.0 or less, the hydrocarbon polymercomponent of the composition of this invention may comprise anelastomeric copolymer of ethylene and propylene and, optionally, anon-conjugated diene monomer, for example, 1,4-hexadiene, or, ingeneral, any thermoplastic hydrocarbon polymer obtained by thehomopolymerization or copolymerization of a monoolefin(s) of the formulaCH₂ ═CHR, where R is H or an alkyl radical, usually of not more thaneight carbon atoms. In particular, this invention is applicable topolyethylene, both of the high density type and the low density type,for example, densities within the range 0.89 to 0.97; polypropylene;polybutene-1; poly(3-methylbutene); poly(methylpentene); and linear lowdensity copolymers of ethylene and an alpha-olefin such as propylene,butene-1, octene-1, decene-1, octadecene, etc. Similarly, the inventionis also applicable to blends of difficultly melt-processible polymers,and difficultly melt-processible polymers containing additives, such asantioxidants, light stabilizers, antiblocking agents, pigments, etc.

Because of the different melt characteristics of the differenthydrocarbon polymers mentioned, the addition of the types (1) and (2)fluorocarbon polymers may be of greater value in some hydrocarbonpolymers than in others. Thus, hydrocarbon polymers such aspolypropylene and branched polyethylene, that are not of high molecularweight have good melt flow characteristics even at low temperatures, sothat surface roughness and other surface defects can be avoided byadjustment of extrusion conditions. Such hydrocarbon polymers may notrequire the use of the fluorocarbon polymer additives of this invention,or be noticeably improved by them, except under unusual, adverseextrusion conditions. Such hydrocarbon polymers, therefore, areconsidered herein as not difficultly melt-processible polymers. However,other polymers such a high molecular weight, high density polyethyleneor linear low density polyethylene copolymers, particularly those withnarrow molecular weight distributions, do not have this degree offreedom in the variation of extrusion conditions and it is particularlywith these resins that remarkable improvements in the surface quality ofthe extruded product are obtained with compositions containing thedescribed type (1) and type (2) fluorocarbon polymers.

It will also be recognized by one skilled in the art that it may not bepossible to achieve, simultaneously, reduced die pressure, increasedthroughput and improved surface quality to the maximum extent at givenconcentration of types (1) and (2). Thus, one might elect to attainmaximum improvement in one parameter, in particular, at the expense ofcorresponding improvements in other parameters. For example, increasedoutput of extrudate with high quality surface characteristics may notnecessarily be accompanied by reduced die pressure. The best set ofconditions will be determined by the specific requirements of theextrusion.

The addition of the fluorocarbon polymer modifiers to the difficultlymelt-processible polymer can be accomplished by any of the meansheretofore developed for the addition of modifiers to such polymers. Forexample, the fluorocarbon polymers (1) and (2) may be addedindependently to, for example, a hydrocarbon polymer on a rubbercompounding mill or in a Banbury or other internal mixer or in a mixingextruder, in all of which the fluorocarbon polymers are uniformlydistributed throughout the host polymer. It is also feasible todry-blend the two fluoropolymers with the host polymer in the solidstate, and then effect uniform distribution of the fluoropolymers in themelt extruder employed in the fabrication by using an extruder screwwith good mixing capability.

Alternatively, masterbatch dispersions (mixtures) of types (1) and (2)in a diluent polymer, either together or separately, can be metered tothe feed section of the extruder by appropriate devices. The diluentpolymer can be a difficultly melt-processible polymer, or it can be amelt-processible polymer that does not substantially deleteriouslyaffect the interaction of the aforesaid components (a), (b)(1) and(b)(2) in achieving the beneficial effects of the invention. Forexample, the diluent polymer can be a melt-processible hydrocarbonpolymer, such as a homopolymer or copolymer of a monoolefin(s) of theformula RCH═CH₂ wherein R is H or an alkyl radical, usually of not morethan eight carbon atoms. In most cases such a hydrocarbon polymer willhave a melt index (ASTM D-1238) at 190° C. of 20.0 or less, preferably5.0 or less. In preparing such masterbatches the amounts of fluorocarbono polymers types (1) and (2) will usually be such that they provide 1-25wt. %, preferably 1-10 wt. %, of the masterbatch. Further to the aboveregarding the need to avoid adversely affecting the beneficial effectsof the invention, in preparing the masterbatch, the concentrations oftypes (1) and (2), as well as the diluent polymer, will be selected soas to achieve good mixing of all the ingredients. Particularly,fibrillation of the fluorocarbon polymer type (2) is to be avoided. Inany of the above procedures, it is also possible to employ previouslyprepared mixtures of fluorocarbon polymer type (1) with fluorocarbonpolymer type (2).

In the practice of this invention, it will be found that the beneficialeffects are not necessarily observed immediately on the onset ofextrusion, and depending on the overall concentrations of modifier, itmay take from 10 minutes to 8 hours to reach stable extrusion rate anddie pressure. Longer times are required at low concentrations of types(1) and (2). When it is desirable to operate at very low levels ofmodifiers and hasten the achievement of equilibrium, it may be expedientto first "condition" the extruder rapidly using a composition containing0.1 to 1wt. % of the fluorocarbon polymers types (1) and (2), and thento switch to the desired concentrations of types (1) and (2).

Just as it has been observed that the beneficial effects may not beobserved immediately, it has also been observed that the beneficialeffects may continue to be observed after addition of the fluorocarbonpolymers of types (1) and (2) is discontinued. Consistent with thisobservation, after stable extrusion rate and die pressure are achieved,the beneficial effects of the invention may be realized by alternating afeed of difficultly melt-processible polymer and one containing theprocessing aid of the invention.

The evaluations reported below employ a C. W. Brabender ComputerizedPlasti-Corder equipped with a 19.1 mm (3/4 in.) diameter extruder with a25/1 length/diameter ratio. The screw has ten feed flights, 10compression flights with a compression ratio of 3:1, and 5 meteringflights. Operating parameters are controlled by five independent heatingzones (No. 5 closest to the die), four pressure transducers and atorque-measuring drive unit with 1-120 rpm capability. The instrument isequipped with software for rheometric capillary extrusion testing. Thecapillary die, made from #416 nitrided stainless steel, has a diameterof 2 mm and a length of 40 mm, unless otherwise noted. In operation, therequired machine conditions are set and the polymer is then extruded,usually at 40 rpm, until equilibrium (constant throughput and constantdie pressure) is reached. For a linear low density polyethylene with amelt index at 190° C. of 1, extrusion at 40 rpm at 204° C. gives athroughput of about 19-20 g/min. and a die pressure of 28 MPa(Comparative Example 1). For experiments that are run in sequence, bychanging the feed composition, the initial output parameters correspondto the previous equilibrium, and then gradually change to a newequilibrium. When equilibrium is achieved a range of screw speeds isthen run to produce new equilibrium values of throughput and diepressure. The relation between throughput and die pressure is determinedfrom a plot of the data, and die pressure data at certain fixedproduction rates can be estimated for comparison of data betweenexperiments. Surface quality of the extrudate is judged by visualexamination.

After each run the extruder is thoroughly cleaned. The equipment isfirst purged with a highly filled abrasive composition, for example, thecommercially available UCC-DFD-0964. The capillary die is removed andheated with a propane torch until it is free of polymer and has reacheda red glow. The extruder is disassembled and each section--screw,barrel, die assembly, and transducers--is cleaned, first with a wirebrush, and then with methyl ethyl ketone solvent. After reassembly andcalibration of the transducers, the unmodified hydrocarbon polymer isrun first to establish equilibrium conditions, and to assure thatreliable output is being obtained. For this purpose, the equilibriumvalue at 40 rpm, only, was sometimes used. If previously establishedequilibrium values for unmodified polymer are not achieved, the cleanoutprocedure is repeated.

In Table 1 the various materials used in the examples which follow areidentified.

EXAMPLES Comparative Example 1

Hydrocarbon Polymer A was introduced to the extruder with the screwoperating at 40 rpm and heating zones Nos. 1, 2, 3, 4 and 5 controllingat nominal temperature settings of 150°, 180°, 200°, 204°, and 204° C.,respectively (No. 5 is closest to the die). Equilibrium extrusionconditions, when throughput and die pressure were constant, were reachedafter a period of 15 min. The screw rpm was then systematically variedfrom 12 rpm to 60 rpm. After determining the extrusion rate at variousscrew speeds, the data were input to a computer program which generateda curve of die pressure vs. throughput (shown in Curve 1 of the Figurewhich is a part of this specification). Selected values taken from Curve1are shown in Table 2. The extrudates of Hydrocarbon Polymer A hadsurface roughness at all extrusion rates above about 4 g/min.

Comparative Example 2

Hydrocarbon Polymer A which, as a dry blend, had intimately dispersedtherein 0.1% of Fluorocarbon Polymer 2A, was added to the extruder justat the end of Comparative Example 1, at the same nominal temperaturesettings and at a screw speed of 40 rpm. Steady state was achieved after10 min. and did not change after a further 240 min. The diepressure/throughput relationship was then obtained as in ComparativeExample 1 and is shown in Curve 2 of the Figure. Data are shown in Table2. There was no significant effect of Fluorocarbon Polymer 2A, alone, onthe flow characteristics of Hydrocarbon Polymer A, and surface roughnessappeared at all extrusion rates above about 4 g/min.

Comparative Example 3

An extruder warm-up was carried out as in Comparative Example 1 withunmodified Hydrocarbon Polymer A, giving the same results. HydrocarbonPolymer A which, as a dry blend, had intimately dispersed therein 0.02wt. % of Fluorocarbon Polymer 1A, was then added to the extruder at thesame temperature settings and at a screw speed of 40 rpm. Steady statewas achieved after 60 min. and did not change after a further 60 min.The die pressure/throughput relationship was then obtained as inComparative Example 1 and is shown as Curve 3 in the Figure.Representative data are shown in Table 2. In this case there was anapproximate 10% reduction in die pressure at a given throughput,compared to Comparative Example 1, and extrudates were smooth and glossyat extrusion rates below about 30 g/min.

Example 1

An extruder warm-up was carried out as in Comparative Example 1, givingthe same results. Hydrocarbon Polymer A which, as a dry blend, hadintimately dispersed therein 0.01 wt. % of Fluorocarbon Polymer lA and0.01 wt. % of Fluorocarbon Polymer 2A was then added at the sametemperature settings and a screw speed of 40 rpm. A new equilibrium wasestablished, after 180 min., at much lower pressures than for thehydrocarbon resin alone or for the composition of Comparative Example 3.The die pressure/throughput curve was then obtained as in ComparativeExample 1, and is shown as Curve 4 in the Figure. Representative dataare shown in Table 2. There was an approximately 30% drop in diepressure over the entire range, compared to Hydrocarbon Polymer A, eventhough the combined concentrations of Fluorocarbon Polymers 1A and 2A inthis example is no greater than the concentration of FluorocarbonPolymer lA in Comparative Example 3. Extrudate surfaces were smooth andglossy throughout the range of extrusion rates attainable under theconditions of the example (up to 55 g/min., which is equivalent to ashear rate of about 1500 sec⁻¹). When a 1.5 mm diameter die was used inorder to obtain shear rates up to about 3000 sec⁻¹, the extrudate wassmooth and glossy over the entire range of extrusion rates.

Example 2

An extruder warm-up was carried out as in Example 1, with similarresults. A dry blend of Hydrocarbon Polymer A having intimatelydispersed therein 0.0005 wt. % of Fluorocarbon Polymer 1A and 0.0020 wt.% of Fluorocarbon Polymer 2A was then added at the same temperaturesettings and a screw speed of 40 rpm. The new equilibrium wasestablished after 180 minutes, at a lower die pressure than for thehydrocarbon resin alone or for the composition of Comparative Example 3.The die pressure/extrusion rate curve was obtained as in Example 1 andrepresentative data are shown in Table 2. There was an approximately 28%reduction in die pressure over the entire extrusion rate range comparedto Hydrocarbon Polymer A, even though the combined concentrations ofFluorocarbon Polymers 1A and 2A is only 12.5% of the concentration ofFluorocarbon Polymer 1A in Comparative Example 3. Extrudate surfaceswere smooth and glossy at extrusion rates below 55 g/min.

Example 3

In this example a series of compositions was evaluated to demonstratethe effect of the relative weight ratios of Fluorocarbon Polymer 1A toFluorocarbon Polymer 2A, as shown in Table 3. Each composition was a dryblend of Fluorocarbon Polymers 1A and 2A in Hydrocarbon Polymer A, andafter extruder warm-up as described in Example 1, each was added at thesame temperature settings and a screw speed of 40 rpm. New equilibriawere then established after 180 minutes, at lower die pressures than forthe hydrocarbon resin alone or for the composition of ComparativeExample 3. Die pressure/extrusion rate data were obtained as in Example1 and are shown in Table 3. There is a significant reduction in diepressure over the entire range compared to Hydrocarbon Polymer A, eventhough the combined concentrations of Fluorocarbon Polymers 1A and 2A isno greater than the concentration in Comparative Example 3. Extrudatesurfaces were smooth and glossy at extrusion rates up to 55 g/min.

Example 4

A composition of Hydrocarbon Polymer A containing an intimate dry powdermix of Fluorocarbon Polymers 1B and 2A, 0.01 wt. % of each, based ondifficultly melt-processible polymer, was extruded and evaluated as inExample 1. A control experiment in which the difficultlymelt-processible polymer contained 0.04 wt. % of Fluorocarbon Polymer1B, alone, was also carried out. Data in Table 4 show that thecomposition of this invention extrudes at very much lower die pressuresthan the control and the extrudate is free of surface imperfections atmuch higher extrusion rates, even though it contains only half as muchtotal modifier.

Example 5

A composition of Hydrocarbon Polymer A containing an intimate dry powdermix of Fluorocarbon Polymers 1C and 2A, 0.01 wt. % of each, based onhydrocarbon polymer, was extruded and evaluated as in Example 1. Acontrol experiment in which the hydrocarbon polymer contained 0.04 partby wt. of Fluorocarbon Polymer 1C, alone, was also carried out. Data inTable 4 show that the composition of this example extrudes at very muchlower die pressures than the control and the extrudate is free ofsurface imperfections at much higher extrusion rates, even though itcontains only half as much total modifier.

Examples 6-10

For each example, Hydrocarbon Polymer A, which as a dry blend hadintimately dispersed therein 0.01 wt. % of Fluorocarbon Polymer 1A and0.01 wt. % of Fluorocarbon Polymers 2B, 2C., 2D, 2E, or 2F (Examples6-10, respectively), was added to the extruder and treated in the mannerdescribed in Example 1. As shown by the data in Table 5, the newequilibria were then established after 180 minutes, at lower pressuresthan for the controls represented by Comparative Examples 1 and 3, Table2. All extrudate surfaces were smooth and glossy throughout the range ofextrusion rates up to 38 g/min. Compositions of Hydrocarbon Polymer Aand 0.10 wt. % of any of the Fluorocarbon Polymers 2B, 2C., 2D, 2E and2F, or 2F alone, showed no improvement in extrusion behavior (data notshown).

Examples 11 and 12

In these examples Hydrocarbon Polymers B and C were compared informulations containing dry blends of Fluorocarbon Polymers 1A and 2A inthe amounts shown in Table 6. Die pressure/extrusion rate data wereevaluated as outlined in Example 1. For each example there is a controlsample containing no additives and another showing the effect ofFluorocarbon Polymer 1A alone. Data were analyzed as in Example 1 andare shown in Table 6.

Example 13

In this experiment a chrome-plated, 2.54 cm (1 in.) wide slit die havinga gap of 0.76 mm (0.03 in.) and a land length of 1.27 cm (0.5 in.) wasused. A dry blend composition of Hydrocarbon Polymer A and 0.01 wt. % ofeach of Fluorocarbon Polymers 1A and 2A was fed at 60 rpm, giving theinitial throughput and die pressure ratings indicated in Table 7. Theinitial extrudate had a rough dull surface. After 3 h the extrudate wassmooth and glossy and there was a 17.5% reduction in die pressure aswell as a 3.5% increase in throughput. The extrudate surface remainedexcellent up to the maximum throughput achievable with the extruder (55g/min. at 120 rpm). In a similarly-run control experiment withHydrocarbon Polymer A alone, the starting and final parameters were asshown in Table 7, and the extrudate had a dull rough surface at allextrusion rates above about 8 g/min. In another control experiment with0.02 wt.% of Fluorocarbon Polymer 1A, there was only a 3% pressure dropafter 3 h and nil increase in throughput. The extrudate surface wassmooth and glossy at 60 rpm, but dull and rough in appearance at allhigher screw speeds.

                  TABLE 1                                                         ______________________________________                                         All are amorphous at room temperature and above.                             ______________________________________                                        Type (1) Fluorocarbon Polymers:                                               1A:     A commercially available fluoroelastomer                                      containing polymer repeat units of 60 wt. %                                   vinylidene fluoride and 40 wt. %                                              hexafluoropropylene and having a Mooney                                       viscosity of 60 at 121° C. It was in the                               form of a fine powder which had been                                          obtained by cryogenic grinding and had a                                      light dusting of calcium carbonate as an                                      antiblocking agent.                                                   1B:     A commercially available fluoroelastomer                                      containing polymer repeat units of 45 wt. %                                   vinylidene fluoride, 30 wt. %                                                 hexafluoropropylene and 25 wt. %                                              tetrafluoroethylene and having a Mooney                                       viscosity of 80 at 121° C. It was ground and                           dusted as in 1A.                                                      1C:     A commercially available copolymer composed                                   of polymer repeat units of                                                    tetrafluoroethylene, propylene and                                            vinylidene fluoride.                                                  Type (2) Fluorocarbon Polymers:                                               2A:     A commercially available PTFE resin which                                     has been irradiated, melts at 280° C., and has                         an average particle size of about 1 mm.                               2B:     A commercially available, high molecular                                      weight, non-melt-processible PTFE, prepared                                   by suspension polymerization, having a                                        standard specific gravity of 2.16 and an                                      average particle size of 35 micrometers.                              2C:     A commercially available powdered copolymer                                   of tetrafluoroethylene and 12 wt. % of                                        hexafluoropropylene and having a melt                                         viscosity of 9,500 Ns/m.sup.2 at 372° C.                       2D:     A commercially available powdered copolymer                                   of tetrafluoroethylene and 3-4 wt. % of                                       perfluoro(propyl vinyl ether) and having a                                    melt viscosity of 4,700 Ns/m.sup.2 at 372° C.                  2E:     A commercially available powdered copolymer                                   of tetrafluoroethylene and 3-4 wt. % of                                       perfluoro(propyl vinyl ether) and having a                                    melt viscosity of 34,000 Ns/m.sup.2 at 372° C.                 2F:     A commercially available powdered,                                            essentially alternating copolymer of                                          tetrafluoroethylene, ethylene and a small                                     amount of a proprietary comonomer, and                                        having a melt flow of 20 at 297° C.                                    (ASTM-D3159).                                                         Hydrocarbon Polymers                                                          A:      A high molecular weight, linear low density                                   (d = 0.918) copolymer of ethylene and butene-1                                having a melt index (ASTM D-1238, cond. E)                                    of 1.0.                                                               B:      A high density polyethylene (d =  0.945) having                               a melt index of 0.05.                                                 C:      A low density (d = 0.925) polyethylene                                        containing 5 wt. % of high density                                            polyethylene and a small quantity of                                          poly(vinyl acetate), and having a melt index                                  of 0.50.                                                              ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________                  Comparative Examples                                                                            Example                                                                            Example                                  EXAMPLES      1     2     3     1    2                                        __________________________________________________________________________    COMPOSITION (% by wt.)                                                        Hydrocarbon Polymer A                                                                       100   99.9  99.95 99.98                                                                              99.975                                   Fluorocarbon Polymer 2A                                                                     --    0.1   --    0.01 0.002                                    Fluorocarbon Polymer 1A                                                                     --    --    0.02  0.01 0.0005                                   Throughput (g/min.)                                                                         Die Pressure (MPa)                                              2.1           9.9                                                             5.0           16.4              11.7                                          7.9           20.4  20.2  18.6  14.3                                          10.0          22.1  22.1  19.6  15.6 14.9                                     15.0          26.3  26.3  24.1  18.9 18.0                                     20.0          29.1  29.1  27.0  21.1 20.2                                     25.0          31.3  31.3  29.5  23.4 22.4                                     30.0          33.5  33.4  31.7  25.4 24.5                                     35.0          34.3        33.7  26.9                                          40.0          35.4              28.3                                          45.0          35.8              29.4                                          50.0                            30.4                                          55.0                            30.9                                          Surface       R, D above                                                                          R,D above                                                                           S,G at                                                                              S,G to                                                                             S, G to                                                4 g/min.                                                                            4 g/min.                                                                            29 g/min.                                                                           55 g/min.                                                                          55 g/min.                                                          and below                                           __________________________________________________________________________     S -- smooth                                                                   G -- glossy                                                                   R -- rough                                                                    D -- dull                                                                

                                      TABLE 3                                     __________________________________________________________________________    EXAMPLE 3                                                                                   A    B   C   D   E   F                                          __________________________________________________________________________    COMPOSITION (% by wt.)                                                        Hydrocarbon Polymer A                                                                       99.980                                                                             99.980                                                                            99.980                                                                            99.980                                                                            99.980                                                                            99.980                                     Fluorocarbon Polymer 2A                                                                     0.0196                                                                             0.019                                                                             0.018                                                                             0.016                                                                             0.002                                                                             0.001                                      Fluorocarbon Polymer 1A                                                                     0.0004                                                                             0.001                                                                             0.002                                                                             0.004                                                                             0.018                                                                             0.019                                      Wt. ratio 1A/2A                                                                             2/98 5/95                                                                              10/90                                                                             20/80                                                                             90/10                                                                             95/5                                       Throughput (g/min.)                                                                         Die Pressure (MPa)                                              10            15.1 7.7 8.4 11.5                                                                              18.3                                                                              17.3                                       15            18.5 9.9 10.7                                                                              14.2                                                                              21.8                                                                              21.1                                       20            21.0 11.8                                                                              13.1                                                                              16.3                                                                              24.6                                                                              24.1                                       25            23.3 13.9                                                                              15.8                                                                              18.2                                                                              26.9                                                                              26.8                                       30            25.4 16.0                                                                              18.6                                                                              20.2                                                                              28.8                                                                              29.2                                       Surface       all extrudates were smooth and glossy up to 55                  __________________________________________________________________________                  g/min.                                                      

                                      TABLE 4                                     __________________________________________________________________________                  Control                                                                             Example 4                                                                           Control                                                                             Example 5                                     __________________________________________________________________________    COMPOSITION (% by wt.)                                                        Hydrocarbon Polymer A                                                                       99.96 99.98 99.96 99.98                                         Fluorocarbon Polymer 2A                                                                     --    0.01  --    0.01                                          Fluorocarbon Polymer 1B                                                                     0.04  0.01  --    --                                            Fluorocarbon Polymer 1C                                                                     --    --    0.04  0.01                                          Throughput (g/min.)                                                                         Die Pressure (MPa)                                              10            17.4  8.7   22.3  19.7                                          15            21.5  10.9  26.8  23.6                                          20            24.5  12.7  29.6  26.0                                          25            27.1  14.8  31.7  28.3                                          30            29.4  17.0  33.3  30.4                                          Surface       S, G below                                                                          S, G below                                                                          S, G below                                                                          S, G to                                                     38 g/min.                                                                           55 g/min.                                                                           28 g/min.                                                                           55 g/min.                                     __________________________________________________________________________     S -- smooth                                                                   G -- glossy                                                                   R -- rough                                                                    D -- dull                                                                

                  TABLE 5                                                         ______________________________________                                        Examples         6      7      8    9     10                                  ______________________________________                                        COMPOSITION (% by wt.)                                                        Hydrocarbon Polymer A                                                                          99.98  99.98  99.98                                                                              99.98 99.98                               Fluorocarbon Polymer 1A                                                                        0.01   0.01   0.01 0.01  0.01                                Fluorocarbon Polymer 2B                                                                        0.01   --     --   --    --                                  Fluorocarbon Polymer 2C                                                                        --     0.01   --   --    --                                  Fluorocarbon Polymer 2D                                                                        --     --     0.01 --    --                                  Fluorocarbon Polymer 2E                                                                        --     --     --   0.01  --                                  Fluorocarbon Polymer 2F                                                                        --     --     --   --    0.01                                Throughput (g/min.)                                                                            Die Pressure (MPa)                                           10               19.3   20.0   19.8 19.3  18.4                                15               23.2   22.7   23.8 23.7  22.6                                20               25.9   25.2   27.0 26.7  25.6                                25               28.4   27.6   29.6 29.4  23.3                                30               30.6   29.7   --   31.7  30.7                                Surface          all surfaces smooth and glossy                                                below 38 g/min.                                              ______________________________________                                    

                                      TABLE 6                                     __________________________________________________________________________                  Control                                                                             Control                                                                            Example 11                                                                          Control                                                                            Control                                                                            Example 12                           __________________________________________________________________________    COMPOSITION (% by wt.)                                                        Hydrocarbon Polymer B                                                                       100   99.96                                                                              99.98 --   --   --                                   Hydrocarbon Polymer C                                                                       --    --   --    100  99.92                                                                              99.96                                Fluorocarbon Polymer 1A                                                                     --    0.04 0.01  --   0.08 0.02                                 Fluorocarbon Polymer 2A                                                                     --    --   0.01  --   --   0.02                                 Throughput (g/min.)                                                                         Die Pressure (MPa)                                              10            25.4  19.0 --    --   --   --                                   15            unstable                                                                            19.6 17.9  12.4 11.9 11.5                                 20            unstable                                                                            21.5 19.3  13.6 13.1 12.9                                 25            unstable                                                                            --   --    14.7 14.2 14.0                                 30            unstable                                                                            --   --    15.7 15.0 14.9                                 Surface       R, D above                                                                          S, G to                                                                            S, G to                                                                             S, G to                                                                            S, G to                                                                            S, G to*                                           10 g/min.                                                                           23 g/min.                                                                          23 g/min.                                                                           38 g/min.                                                                          38 g/min.                                                                          38 g/min.                            __________________________________________________________________________     S -- smooth                                                                   G -- glossy                                                                   R -- rough                                                                    D -- dull                                                                     *These extrudates did not have the occasional cloudy streaks that appeare     in the controls.                                                         

                  TABLE 7                                                         ______________________________________                                                       Control                                                                              Control  Example 13                                     ______________________________________                                        COMPOSITION (% by wt.)                                                        Fluorocarbon Polymer 1A                                                                        --       0.02     0.02                                       Fluorocarbon Polymer 2A                                                                        --       --       0.02                                       Starting pressure, MPa                                                                         25.4     25.6     25.1                                       Starting throughput, g/min.                                                                    25.7     24.7     24.7                                       Ending pressure, MPa                                                                           25.4     24.8     19.7                                       Ending throughput, g/min.                                                                      25.7     24.9     25.8                                       Surface          rough    smooth   smooth                                                               glossy   glossy                                     ______________________________________                                    

We claim:
 1. Polymer blend composition having improved processibilityand comprising:(a) a major portion of a difficultly melt-processiblepolymer comprising at least one mono-olefin polymer, and (b) a minorportion of:(1) at least an effective amount, to improve processibility ,of a fluorocarbon copolymer which at the melt-processing temperature of(a) is either in a melted form if crystalline, or is above its glasstransition temperature if amorphous, and (2) at least an effectiveamount, to improve processibility, of at least one tetrafluoroethylenehomopolymer or copolymer of tetrafluoroethylene and at least one monomercopolymerizable therewith, wherein the mole ratio of fluorine tohydrogen is at least 1:1, and which is solid at the melt-processingtemperature of (a).
 2. Composition of claim 1 wherein (a) is ahydrocarbon polymer.
 3. Composition of claim 2 wherein the polymer is ahomopolymer or copolymer of one or more monoolefins of the formulaRCH═CH₂ wherein R is H or alkyl.
 4. Composition of claim 3 wherein alkylis C₁₋₈ alkyl.
 5. Composition of claim 2 wherein the polymer is a highdensity polyethylene.
 6. Composition of claim 2 wherein the polymer is alow density polyethylene.
 7. Composition of claim 2 wherein the polymeris a linear low density polyethylene copolymer.
 8. Composition of claim2 where the polymer is a copolymer comprised of polymer repeat units ofethylene, propylene and a non-conjugated diene.
 9. Composition of claim1 wherein the amount of (b)(1) is no more than 0.5 wt. %, based on theweight of (a).
 10. Composition of claim 9 wherein the amount of (b)(1)is 0.002-0.08 wt. %, based on the weight of (a).
 11. Composition ofclaim 9 wherein the amount of (b)(2) is 0.002-0.08 wt. %, based on theweight of (a).
 12. Composition of claim 1 wherein, in component (b)(1),the mole ratio of fluorine to hydrogen is at least 1:1.5. 13.Composition of claim 1 wherein the melting or softening point ofcomponent (b)(1) is in the range 120°-300 C.. or below.
 14. Compositionof claim 13 wherein the melting or softening point of component (b)(1)is in the range 120°-200° C. or below.
 15. Composition of claim 1wherein component (b)(1) is a fluorocarbon copolymer of vinylidenefluoride, hexafluoropropylene, chlorotrifluoroethylene,tetrafluoroethylene or a perfluoroalkyl perfluorovinyl ether. 16.Composition of claim 15 wherein component (b)(1) is a copolymer ofvinylidene fluoride and a monomer selected from hexafluoropropylene,chlorotrifluoroethylene, 1-hydropentafluoropropylene and2-hydropentafluoropropylene; a copolymer of vinylidene fluoride,tetrafluoroethylene and hexafluoropropylene or 1- or2-hydropentafluoropropylene; or a copolymer of tetrafluoroethylene andpropylene.
 17. Composition of claim 16 wherein the copolymer includespolymer repeat units of a bromo- or iodo group-containing monomer. 18.Composition of claim 1 wherein component (b)(2) ispolytetrafluoroethylene.
 19. Composition of claim 1 wherein component(b)(2) is a copolymer of tetrafluoroethylene and one or more monomersselected from ethylene, a perfluoroolefin, a perfluoro(alkyl vinylether) or a perfluoro(alkyl vinyl ether) containing a functional group.20. Composition of claim 19 wherein the monomer is ethylene. 21.Composition of claim 19 wherein the monomer is hexafluoropropylene. 22.Composition of claim 19 wherein the monomer is perfluoro(propyl vinylether).
 23. Composition of claim 19 wherein the functional group is--SO₂ F or --CO₂ CH₃.
 24. Composition of claim 1 wherein the weightratio of component (b)(1) to component (b)(2) is within the range 2:98to 95:5.
 25. Composition of claim 24 wherein the weight ratio ofcomponent (b)(1) to component (b)(2) is within the range 10:90 to 90:10.26. Processing aid composition for a difficultly melt-processiblepolymer, said composition consisting essentially of:(a) a major portionof a hydrocarbon polymer comprising at least one mono-olefin polymer,and (b) a minor portion of, with the parts totaling 100 parts:(1) 2-95parts by weight of a fluorocarbon copolymer which at the melt-processingtemperature of the difficultly melt-processible polymer is either in amelted form if crystalline or is above its glass transition temperatureif amorphous; and (2) 98-5 parts by weight of a tetrafluoroethylenehomopolymer or copolymer of tetrafluoroethylene and a monomer which iscopolymerizable therewith, wherein the mole ratio of fluorine tohydrogen is at least 1:1, and which is solid at the melt-processingtemperature of the difficulty melt-processible polymer.
 27. Compositionof claim 26 wherein the combined amounts of component (b)(1) andcomponent (b)(2) comprise 1-25 wt. % of the composition.
 28. Compositionof claim 27 wherein the combined amounts of component (b)(1) andcomponent (b)(2) comprise 1-10 wt. % of the composition.
 29. Compositionof claim 26 wherein the hydrocarbon polymer is a difficultymelt-processible polymer.
 30. Composition of claim 26 wherein thehydrocarbon polymer is a homopolymer or copolymer of one or moremonoolefins of the formula RCH═CH₂ wherein R is H or alkyl. 31.Composition of claim 30 wherein alkyl is C₁₋₈ alkyl.
 32. Composition ofclaim 26 wherein the amount of component (b)(1) is 10-90 parts and theamount of component (b)(2) is 90-10 parts.
 33. Composition of claim 26wherein the mole ratio of fluorine to hydrogen in component (b)(1) is atleast 1:1.5.
 34. Composition of claim 26 wherein the melting orsoftening point of component (b)(1) is in the range 120°-300° C. orbelow.
 35. Composition of claim 34 wherein the melting or softeningpoint of component (b)(1) is in the range 120°-200° C. or below. 36.Composition of claim 26 wherein component (b)(1) is a fluorocarboncopolymer of vinylidene fluoride, hexafluoropropylene,chlorotrifluoroethylene, tetrafluoroethylene or a perfluoroalkylperfluorovinyl ether.
 37. Composition of claim 36 wherein component(b)(1) is a copolymer of vinylidene fluoride and a monomer selected fromhexafluoropropylene, chlorotrifluoroethylene,1-hydropentafluoropropylene and 2-hydropentafluoropropylene; a copolymerof vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene or1- or 2-hydropentafluoropropylene; or a copolymer of tetrafluoroethyleneand propylene.
 38. Compositon of claim 37 wherein the copolymer includespolymer repeat units of a bromo- or iodo group-containing monomer. 39.Composition of claim 26 wherein component (b)(2) ispolytetrafluoroethylene.
 40. Composition of claim 26 wherein component(b)(2) is a copolymer of tetrafluoroethylene and one or more monomersselected from ethylene, a perfluoroolefin, a perfluoro(alkyl vinylether) or a perfluoro(alkyl vinyl ether) containing a functional group.41. Composition of claim 40 wherein the monomer is ethylene. 42.Composition of claim 40 wherein the monomer is hexafluoropropylene. 43.Composition of claim 40 wherein the monomer is perfluoro(propyl vinylether).
 44. Composition of claim 40 wherein the functional group is or--SO₂ F or --CO₂ CH₃.
 45. Extrusion process comprising melt extruding adifficultly melt-processible polymer comprising at least one mono-olefinpolymer and having incorporated therein an effective amount, to improveprocessibility, of a processing aid consisting essentially of, with theparts totaling 100 parts:(a) 2-95 parts by weight of a fluorocarboncopolymer which at the melt-processing temperature of the difficultlymelt-processible polymer is either in a melted form if crystalline or isabove its glass transition temperature if amorphous; and (b) 98-5 partsby weight of a tetrafluoroethylene homopolymer or copolymer oftetrafluoroethylene and a monomer which is copolymerizable therewith,wherein the mole ratio of fluorine to hydrogen is at least 1:1, andwhich is solid at the melt-processing temperature of the difficultlymelt-processible polymer.
 46. Process of claim 45 wherein the mole ratioof fluorine to hydrogen in component (a) is at least 1:1.5.
 47. Processof claim 45 wherein the melting or softening point of component (a) isin the range 120°-300° C. or below.
 48. Process of claim 47 wherein themelting or softening point of component (a) is in the range 120°-200° C.or below.
 49. Process of claim 45 wherein component (a) is afluorocarbon copolymer of vinylidene fluoride, hexafluoropropylene,chlorotrifluoroethylene, tetrafluoroethylene or a perfluoroalkylperfluorovinyl ether.
 50. Process of claim 49 wherein component (a) is acopolymer of vinylidene fluoride and a monomer selected fromhexafluoropropylene, chlorotrifluoroethylene,1-hydropentafluoropropylene and 2-hydropentafluoropropylene; a copolymerof vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene or1- or 2-hydropentafluoropropylene; or a copolymer of tetrafluoroethyleneand propylene.
 51. Process of claim 50 wherein the copolymer includespolymer repeat units of a bromo- or iodo group-containing monomer. 52.Process of claim 45 wherein component (b) is polytetrafluoroethylene.53. Process of claim 45 wherein component (b) is a copolymer oftetrafluoroethylene and one or more monomers selected from ethylene, aperfluoroolefin, a perfluoro(alkyl vinyl ether) or a perfluoro(alkylvinyl ether) containing a functional
 54. Process of claim 53 wherein themonomer is ethylene.
 55. Process of claim 53 wherein the monomer ishexafluoropropylene.
 56. Process of claim 53 wherein the monomer isperfluoro(propyl vinyl ether).
 57. Process of claim 53 wherein thefunctional group is --SO₂ F or --CO₂ CH₃.
 58. Process of claim 45wherein the amount of component (a) is 10-90 parts and the amount ofcomponent (b) is 90-10 parts.
 59. Composition of claim 18 wherein thepolytetrafluoroethylene is low molecular weight and non-fibrillating.60. Composition of claim 18 wherein the polytetrafluoroethylene has beensubjected to ionizing radiation.
 61. Composition of claim 39 wherein thepolytetrafluoroethylene is low molecular weight and non-fibrillating.62. Composition of claim 39 wherein the polytetrafluoroethylene has beensubjected to ionizing radiation.
 63. Process of claim 52 wherein thepolytetrafluoroethylene is low molecular weight and non-fibrillating.64. Process of claim 52 wherein the polytetrafluoroethylene has beensubjected to ionizing radiation.